The vaguely-triangular strip of road separating a highway exit from the actual off-ramp. So named because drivers will use the space to stop and make decisions, merge through to the off-ramp after making split-second decisions, and/or crash into water-filled barrels or exit signs contained therein after failing to properly make a decision.

(To a passenger) Did you see that guy cut through the decision lane?
(To another driver) Nice use of the decision lane, idiot!
(Relating a story) Ted really needed to stop, so he parked in the decision lane.
(Relating directions) You can merge off the ramp that's next to the decision lane without any barrels.